Study of the atmospheric circulation during the winter period over the eastern Mediterranean region has been undertaken, in order to develop a map-pattern classification over the area. NCEP Reanalysis data have been used for three levels, geopotential heights at 500 and 850 hPa and sea level pressure data. Daily data spanning a period of 43 years were used for the area 5° to 35° E and 25° to 55° N. A Rotated Principal Component Analysis (RPCA) has been employed, then specifying a maximum and a minimum threshold regarding the PC-scores a number of groups of days were created. Based on these groups of days the dominant circulation patterns over the study area were identified. The influence of these patterns in the Greek area was studied using observational data from twenty-one meteorological stations around Greece. The observational data are composed of mean daily, maximum and minimum temperature, daily range of temperature and precipitation. Using the day-groups, which were identified by the RPCA, the spatial distribution of the observational data was studied and its relationships with the corresponding circulation patterns. Trends and persistence of patterns have been studied with a focus on those that lead to extreme events in the region such as low temperatures and/or heavy precipitation.